Carbonate uranium isotopes record global expansion of marine anoxia during the Toarcian Oceanic Anoxic Event.

Autor: Remírez MN; Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA 22030., Gilleaudeau GJ; Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA 22030., Gan T; Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, VA 22030.; Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742., Kipp MA; Nicholas School of the Environment, Division of Earth and Climate Science, Duke University, Durham, NC 27708., Tissot FLH; The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125., Kaufman AJ; Department of Geology and Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20742., Parente M; Department of Earth Sciences, Environment and Resources, University of Naples Federico II, Naples 80126, Italy.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2024 Jul 02; Vol. 121 (27), pp. e2406032121. Date of Electronic Publication: 2024 Jun 24.
DOI: 10.1073/pnas.2406032121
Abstrakt: The Toarcian Oceanic Anoxic Event (T-OAE; ~183 Mya) was a globally significant carbon-cycle perturbation linked to widespread deposition of organic-rich sediments, massive volcanic CO 2 release, marine faunal extinction, sea-level rise, a crisis in carbonate production related to ocean acidification, and elevated seawater temperatures. Despite recognition of the T-OAE as a potential analog for future ocean deoxygenation, current knowledge on the severity of global ocean anoxia is limited largely to studies of the trace element and isotopic composition of black shales, which are commonly affected by local processes. Here, we present the first carbonate-based uranium isotope (δ 238 U) record of the T-OAE from open marine platform limestones of the southeastern Tethys Ocean as a proxy for global seawater redox conditions. A significant negative δ 238 U excursion (~0.4‰) is recorded just prior to the onset of the negative carbon isotope excursion comprised within the T-OAE, followed by a long-lived recovery of δ 238 U values, thus confirming that the T-OAE represents a global expansion of marine anoxia. Using a Bayesian inverse isotopic mass balance model, we estimate that anoxic waters covered ~6 to 8% of the global seafloor during the peak of the T-OAE, which represents 28 to 38 times the extent of anoxia in the modern ocean. These data, combined with δ 238 U-based estimates of seafloor anoxic area for other CO 2 -driven Phanerozoic OAEs, suggest a common response of ocean anoxia to carbon release, thus improving prediction of future anthropogenically induced ocean deoxygenation.
Competing Interests: Competing interests statement:The authors declare no competing interest.
Databáze: MEDLINE
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